Oxygen evolution and corrosion behaviours of the porous Mn₅Si₃ electrode in sulfuric acid

In this study, the porous Mn₅Si₃ electrodes for metal electrowinning were developed through elemental powders reactive synthesis. The powder size of raw materials and sintering temperature have been changed to study the effect of these fabrication parameters on the pore structure and the electrochemical performance of the porous Mn₅Si₃ electrodes. The effect of Mn ions on the corrosion behaviours of the porous Mn₅Si₃ electrodes has also been investigated. The results indicated that lower sintering temperature in the investigated range led to higher porosity, smaller average pore size and better catalytic activity for oxygen evolution reaction (OER). This phenomenon can be attribute to the larger active surface area of this pore structure. The average pore size increased with the incremental of powder size of Si, however, it appeared that porosity and catalytic activity were almost unchanged, which indicated that pore size has a weak effect on the catalytic activity. Presence of Mn ions in solutions can improve the corrosion resistance of the porous Mn₅Si₃ electrodes, for Mn ions help form an oxide film on the surface of the electrodes, blocking continuous dissolution of the inside Mn₅Si_3. (paper)